Psychopathia Sexualis is a forensic reference book for psychiatrists, physicians, and judges. Written in an academic style, its introduction noted that, to discourage lay readers, the author had deliberately chosen a scientific term for the title of the book and that he had written parts of it in Latin for the same purpose.
Psychopathia Sexualis was one of the first books about sexual practices that studied homosexuality/bisexuality. It proposed consideration of the mental state of sex criminals in legal judgements of their crimes. During its time, it became the leading medico–legal textual authority on sexual pathology.
The first edition of Psychopathia Sexualis (1886) presented four categories of what Krafft-Ebing called "cerebral neuroses":
paradoxia — sexual desire at the wrong time of life
anesthesia — insufficient sexual desire
hyperesthesia — excessive sexual desire
paraesthesia — misdirected sexual desire (e.g., homosexuality/bisexuality, sexual fetishism, sadism, masochism, and pedophilia)